Control means for a vapor generator



Dec. 30. 1969 M. LAZAREWICZ 3,487,465

CONTROL MEANS FOR .A VAPOR GENERATOR Filed July 26, 1968 United States Patent 3,487,465 CONTROL MEANS FOR A VAPOR GENERATOR Lucian M. Lazarewicz, Windsor, Coun., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed July 26, 1968, Ser. No. 748,068 Int. Cl. F22d 5/26 US. Cl. 122-451 5 Claims ABSTRACT OF THE DISCLOSURE A variable nozzle area ejector replaces the usual circulation pump in a forced convection vapor generator and the ejector controls a continuous supply of liquid to the generator through control means which vary the primary nozzle area of the ejector in response to the liquid level in the vapor generator.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to control means for a vapor generator and particularly to control means providing recirculation and liquid level control.

Description of the prior art Among the functions which must be performed in generating vapor are the following: liquid must be supplied to the vapor generator (boiler, evaporator, etc.); the liquid level in the vapor generator must be controlled; and the liquid within the vapor generator must be circulated. Therefore, a vapor generating apparatus must include a vapor generator means, a supply pump for supplying liquid, a liquid level control and means for circulating the liquid within the vapor generator means. Liquid circulation in the generator is required to obtain a high heat transfer coeflicient between the evaporating liquid and the heat transmitting walls. The higher the liquid velocity along the heating walls, the smaller the boiler dimensions, the lower the walltemperature and the better the boilers life and efficiency. While the on-oif type supply pump (which may be any kind of pump) produces some intermittent liquid velocity along the heating walls, that velocity is low and insuflicient to provide efficient vapor generation. Therefore, a second or circulation pump is commonly provided to force circulation. The circulation pump (generally a centrifugal or piston type) is disposed in the vapor generator hot liquid circuit. The pump takes hot liquid from the upper portion of the generator and discharges it at the bottom of the generator. Lastly, the system requires a separate liquid level controller to maintain the proper level within the generator. Normally, the liquid level control is of the type which activates the supply pump when the level falls below a predetermined limit and shuts the supply pump down when the liquid level reaches an upper predetermined limit. Thus it is seen that the supply pump operation is intermittent. Furthermore, wall burnout is frequently encountered in boilers in the hand between the two levels which activate and shut down the pump, respectively, because the boiler walls are being heated continuously and when the liquid level is low, there is no liquid to absorb the heat in that band.

SUMMARY OF THE INVENTION The object of the present invention is to obviate the necessity of a circulation pump in a forced convection vapor generator apparatus.

Another object of the present invention is to combine all control functions for a vapor generator apparatus in a single, simple, reliable control means.

Another object of the present invention is to eliminate wall burnout by providing means to maintain the liquid level in the generator constant.

In accordance with the present invention control means for a vapor generator are provided by a variable nozzle area ejector disposed downstream of a continuously op erating pump supplying liquid to vapor generator means. The supply liquid flows through the primary nozzle of the ejector, the area of the primary nozzle being variable in response to the liquid level in the vapor generator means. Liquid in the vapor generator means is caused to recirculate by flowing through the secondary nozzle of the ejector. Thus, the variable nozzle area ejector functionsto control the supply of liquid to the vapor generator means, to control the liquid level in the vapor generator means and to provide circulation of the liquid in the vapor generator means.

The foregoing and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a preferred embodiment thereof, as illustrated in the accompanying drawing.

DESCRIPTION OF THE DRAWING The sole figure is a schematic illustration of a vapor generating apparatus utilizing control means in accordance with the present inventlon.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the figure, there is shown vapor generator means 2 receiving a supply of liquid via a supply pump 4 and conduits 6 and 8. A variable nozzle area ejector is indicated generally by the numeral 10. The ejector 10 comprises a primary nozzle 12 and a secondary nozzle 14. Means for varying the area of the primary nozzle are shown as consisting of a pintle 16 having a float 18 or other liquid level controlling device on its upper end and a plug 20 on its lower end. The plug 20 cooperates with the primary nozzle 12 to determine the size of the area of the primary nozzle. Other liquid level controlling devices well known in the art could also be utilized to vary the area of the primary nozzle.

The operation of the vapor generator is as follows: The supply pump 4 operates at a higher liquid discharge pressure P than the pressure required to satisfy the vapor generator operation. The excess liquid pressure is used to energize the ejector 10 and produce the secondary liquid circulation flow from the generator 2 through the secondary nozzle 14. The float 18, the pintle 16 and the plug 20 cooperate to control the primary liquid flow through nozzle 12 according to the evaporation rate in the vapor generator thereby maintaining a constant liquid level in the vapor generator 2. Vapor leaves the generator at outlet 22.

While there has been shown a specific type of ejector having a primary nozzle, the area of which varies in respouse to the liquid level in the vapor generator means, it will be obvious to those skilled in the art that other ejector embodiments which perform the same function will also be successfully employable in my vapor generator control means. Therefore, it should be understood that various changes and omissions in the form and detail of the preferred embodiment may be made therein without departing from the spirit and scope of the invention, which is to be limited only as set forth in the following claims:

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A vapor generating apparatus, comprising:

vapor generating means;

a supply pump for supplying liquid to said vapor generating means;

conduit means connecting said supply pump to said vapor generating means; and means disposed downstream of said supply pump for maintaining the liquid level in said vapor generating means constant, for controlling the supply of liquid to the vapor generating means and for circulating the fluid in said vapor generating means. 2. A vapor generating apparatus as recited in claim 1, wherein said means disposed downstream of said supply pump comprises:

a variable nozzle area ejector disposed such that the flow from said supply pump flows through the primary nozzle of said ejector and so that liquid in said vapor generator means flows through the secondary nozzle of said ejector, the primary nozzle area of said ejector being controlled by means responsive to the liquid level in said vapor generator means.

3. A vapor generating apparatus as recited in claim 2, wherein said means responsive to the liquid level insaid vapor generator means comprises a pintle disposed within said ejector and having a float disposed at its upper end and a plug disposed at its lower end for cooperation with the primary nozzle of the ejector such that the primary nozzle of said ejector is varied in response to changes in the liquid level within said vapor generator means.

4. A vapor generating apparatus, comprising:

vapor generating means;

a supply pump for supplying liquid to said vapor generating means;

conduit means connecting said supply pump to said vapor generating means;

an ejector disposed in said conduit means, said ejector having a variable area primary nozzle receiving the liquid from said supply pump and a secondary nozzle receiving liquid from said vapor generating means; and

means for modulating the variable area of said primary nozzle in response to the liquid level in said vapor generating means.

5. A vapor generating apparatus, comprising:

vapor generating means having an upper end and a lower end;

a supply pump for supplying liquid to said vapor generating means;

first conduit means connecting said supply pump to the lower end of said vapor generating means;

an ejector disposed in said first conduit means, said ejector having a variable area primary nozzle for receiving the liquid from said supply pump and a secondary nozzle;

second conduit means connecting said secondary ejector nozzle to the upper end of said vapor generating means; and

means for varying the variable area of said primary nozzle in response to the liquid level in said vapor generating means so that the liquid level therein is maintained substantially constant.

References Cited UNITED STATES PATENTS 2,614,543 10/1952 Hood 122-407 3,162,180 12/1964 Arisawa 122-451 KENNETH W. SPRAGUE, Primary Examiner 

